Lidar observations of sporadic Na layers over Wuhan (30.5°N, 114.4°E)

Abstract

Based on lidar measurements between March and September 2001, the characteristics of sporadic Na layers (Nas layers) over Wuhan (30.5°N, 114.4°E) are presented. Nas layers were observed on 29 occasions from 275 h observational data. They tended to show a seasonal variation with a maximum occurrence rate in July. The maximum Na density was 24080 cm−3 which was comparable with those observed at low and high latitudes. Different from the observations at all other sites over the world, most Nas layers over Wuhan tended to occur around the peak altitudes of the normal Na layers (∼92 km). However, a Nas layer was observed at 112.9 km altitude. The formation of the Nas layers over Wuhan generally needed a longer time than those at low and high latitudes. The formation processes usually consisted of consecutive density enhancement bursts. The Nas layers often exhibited broader layer widths than those at low and high latitudes.